To be fair, I believe the cameraman originally started filming in order to record his dog playing, but then the focus of the video changed. At least on my phone, once you start recording a video, you can't just change the orientation. If you did that, the video itself would rotate instead of the orientation, so you'd have a sideways landscape video.

Beauty is in the eye of the beholder. To me it looks like in this portrait orientation we are getting a bunch of cabinet and floor with jerky back and forth to take in both the dog and the TV. Whereas in landscape, the same orientation as our eyes, we could comfortably appreciate the dog and the TV at the same time.

The obnoxious panning would still be necessary in landscape mode, and for short videos that are supposed to be watched on a smartphone screen portrait mode is a thousand times more logical. The decision of using a frame wider than it is tall for shooting films was originally made to improve immersion as your eyesight is also wide, but immersion isn't a big factor when using a phone. Convenience is.

The sub for sideways recordings, cameramen with parkinson, videos with horible focus or where the cameraman has an zoom fetish. Here you can see videos of interesting/entertaining things but the cameraman is doing such a bad job you want to physically hurt him.